Laser pointing sighting system with designator range finder

ABSTRACT

The invention concerns a laser pointing sighting system comprising a designator range finder ( 19 ) including means (E) for emitting a designating laser beam and reception means (R) for detecting and processing the reflection of a hot spot formed by said beam on a target, said reception means (R) are capable in the absence of designating beam emission by the range finder, of detecting the reflection of a hot spot formed on a target by a third designating device, the system comprising means capable, when the reception means detect such a hot spot, of being automatically oriented relative to the direction defined by said spot.

GENERAL FIELD AND PRIOR ART

[0001] The invention relates to laser designator/rangefinder sightingsystems.

[0002] Conventionally, sighting systems of the designator/viewfindertype are known, these comprising, in addition to a purely opticalviewing and sighting channel, one or more TV or IR camera displaychannels, together with a laser emission/receive channel that is usedboth for the rangefinding function and for the designating function.

[0003] In general, these sighting systems operate in “autonomous” mode:the laser channel of the rangefinder is used to illuminate a target thatit is desired to designate with a laser-guided weapon that is fired bythe vehicle equipped with the sighting system and that is guided ontothe laser spot formed on the target.

[0004] Also known are sighting systems in which the target is designatedin “cooperative” mode: the target is then illuminated by means differentfrom those of the vehicle that carries and fires the guided weapon. Forthis mode of operation, it is then necessary for the sighting system ofthis vehicle to have means allowing it to detect the illumination spoton the target and to slave its line of sight to this spot so that theguided weapon is fired in the direction of the designated target andonly when the latter is effectively illuminated.

[0005] At the present time, sighting systems that allow operation incooperative mode are relatively complex. They incorporate means formeasuring differences with respect to the laser spot, which means arespecifically dedicated to this function and are juxtaposed on thevarious other channels of the sighting system, being very specificallytwinned with said other channels, thereby complicating the design of thesystems and increasing the volume, weight and cost thereof.

PRESENTATION OF THE INVENTION

[0006] The invention proposes a sighting system that is capable ofoperating in autonomous mode and in cooperative mode and that does nothave the drawbacks of the sighting systems that are known at the presenttime as allowing operation in cooperative mode.

[0007] The proposed sighting system is a laser sighting system, of thetype comprising a designator/rangefinder comprising means for emitting adesignating beam and receive means for detecting and processing thereflection of a light spot formed by said beam on a target,characterized in that said receive means are capable, in the absence ofa designating beam being emitted by the rangefinder, of detecting thereflection of a light spot formed on a target by a third-partydesignating device, the system including means capable, when the receivemeans of the rangefinder detect such a light spot, of beingautomatically oriented in relation to the direction defined by saidspot.

[0008] It will be noted that such a system has the advantage of allowingoperation in cooperative mode without requiring optical channels anddetectors other than those generally present in sighting systems.

[0009] Such a system is also advantageously supplemented by thefollowing various features taken individually or in their technicallypossible combinations:

[0010] it includes means capable of slaving the line of sight to thelight spot detected by the receive means of the rangefinder;

[0011] the slaving means include means capable of introducingperturbations in the viewing direction of the rangefinder and of slavingthis direction to the maximum detection flux received by the receivemeans of the rangefinder;

[0012] it includes a camera display channel, the viewing direction ofwhich is aligned with the viewing direction of the rangefinder, therangefinder channel and the display channel being partly common;

[0013] the field of view of the rangefinder channel is of the order of 1mrad;

[0014] the perturbations in the line of sight correspond toperturbations of the order of 1 to 10 pixels on the image recorded bythe camera;

[0015] it includes means for slaving the line of sight by automatictracking prior to a light spot being detected by the rangefinder;

[0016] it includes means capable of verifying a wavelength and/or a codeon the light spot detected. The invention also proposes a method ofdesignating a target, characterized in that it involves:

[0017] positioning of the target in the field of view of a system of theaforementioned type;

[0018] emission of a laser beam by a third-party designator onto thetarget;

[0019] detection of the spot formed on the target by said beam; and

[0020] locking of the target designated by the sighting system.

[0021] Especially advantageously, the target is positioned in the fieldof view by automatic tracking.

[0022] The invention also proposes a fire control system, characterizedin that it includes a sighting system of the aforementioned type and inthat the system includes means capable of authorizing the firing of theweapon when the receive means of the rangefinder detect such a lightspot.

PRESENTATION OF THE FIGURES

[0023] Other features and advantages of the invention will becomeapparent during the description below of a preferred embodiment. In theappended drawings:

[0024]FIG. 1 is a schematic representation of an optical structure of asighting/fire control system according to one possible embodiment of theinvention;

[0025]FIG. 2 is a diagram showing the principle of the preferredembodiment of the invention; and

[0026]FIG. 3 is a diagram showing the principle of the operation of thecooperative mode of the preferred embodiment of the invention.

DESCRIPTION OF ONE OR MORE POSSIBLE EMBODIMENTS

[0027] Optical Structure

[0028]FIG. 1 shows the optical arrangement of the rangefinder and TVchannels of a sighting/fire control system with the general reference100.

[0029] This arrangement includes an optical head that is common to theTV and rangefinder channels and that comprises an entry window 1, finestabilization means 2, a front lens 4 and deflection mirrors (frontmirror 3 and mirror 6).

[0030] It also includes a dichroic mirror 7 that delivers the lightbeams received by the optical head, on the one hand, to optical meansspecific to the TV channel and, on the other hand, to optical meansspecific to the rangefinder channel.

[0031] In the example illustrated in FIG. 1, the means specific to theTV channel include a lens 8 and a deflection mirror 9 that send theimage received by the plate 7 as input for a camera 11, which is forexample a camera 11 which is for example a TV camera, but which may alsobe an IR camera.

[0032] The means specific to the rangefinder channel include a splittercube 14 that sends, via a convergent lens 12, the light beams receivedfrom the dichroic plate 7 onto receive means R of a rangefinder 19 andthat receives, from emission means E of this rangefinder, the laser-typebeam emitted by the latter, the beam emitted by the rangefinder passingthrough said dichroic cube 14 in order to be sent via the mirror 7 ontothe optical head of the sighting/fire control system.

[0033] In FIG. 1, the references 15, 17 and 20 denote deflection mirrorsof the emission and receive channels of the rangefinder.

[0034] Of course, many optical configurations other than that shown inFIG. 1 would be conceivable.

[0035] In particular, the camera 11 and the rangefinder 19 may have nocommon channel. However, common-channel architectures are preferred if alaser rangefinder receive field is particularly narrow (typically 1mrad) compared with the field of a camera (some twenty mrads).

[0036] Processing

[0037] Apart from an optical structure of the type shown in FIG. 1, asystem according to one possible embodiment of the invention includesprocessing means T that are capable of managing the operation inautonomous mode of the rangefinder 19 (block 120 in FIG. 2) and itsoperation in cooperative mode (block 110), which means are furthermorecapable of managing the slaving of the line of sight and of the firingdirection for one and the other of the two operating modes (fire control130).

[0038] In autonomous mode, the direction in which the weapon is aimed isslaved by the fire control to the line of sight, which corresponds tothe designating direction of the rangefinder.

[0039] In cooperative mode, the rangefinder operates only as receiverand emits no designating beam.

[0040] It aims in the viewing direction and line of sight observed bythe optical head of the system, if necessary creating smallperturbations around this direction.

[0041] When the rangefinder 19 detects a laser spot in the directionthat it is viewing, the processing means T verify that this laser spotcorresponds the wavelength and/or to the code expected for a designatingspot.

[0042] If this is actually the case, the processing means T slave theline of sight and the firing direction to the direction in which therangefinder is aimed.

[0043]FIG. 3 illustrates schematically means that allow the processingmeans T to operate in cooperative mode (block 110).

[0044] These means comprise means 112 that analyze the light fluxreceived by the detection means R of the rangefinder and operate motordrive means 111 that allow the line of sight to be moved in elevationand in bearing.

[0045] These means 112 act in particular on the motor drive means 111 soas to apply small perturbations to the line of sight and to slave thelatter to the position corresponding to a maximum detection flux.

[0046] The expression “small perturbations” is understood to mean in thepresent text perturbations that correspond to perturbations of the orderof 1 to 10 pixels on the image recorded by the camera 11, making itpossible to vary the signal detected so as to be able to be slaved toits maximum without excessively disturbing the image presented.

[0047] The processing means also include means 113 that analyze thewavelength and/or the phase, frequency or amplitude modulations that arecarried the optical spot detected, in order to verify that this isindeed a designating spot that must allow the firing of the weapon to beauthorized.

[0048] For this purpose, the means 113 make comparisons between thecodes determined by synchronous demodulation of the optical spotdetected and designation codes, that are for example stored in storagemeans 114 provided for this purpose.

[0049] These designating codes may, for example, be NATO (STANAG 3733)codes or any other designation code used for illuminating targets.

[0050] Example of Use

[0051] A system of the type described above is, for example, used in thefollowing manner.

[0052] Firstly, a target to be designated is indicated to the sightingsystem by conventional means, such as GPS coordinates or else navigationcoordinates or else a visual descriptor.

[0053] The sighting system is then slaved by automatic tracking to thetarget thus designated.

[0054] For example, if the target is designated by a visual descriptor,the automatic tracking may be carried out by conventional differencemeasurement or image processing means in the TV or IR channel thatcorresponds to the camera 11, the image recorded by said camera beingdisplayed on a screen (screen 101 in FIG. 2) on which a sightinggraticule also appears. When the sighting system is slaved to the areathat has been indicated thereto, a third-party designator (a soldiernear the target, for example) illuminates the target using a laser-typedesignating beam which is, for example, pulsed according to a defineddesignation code.

[0055] The spot formed on this target by the designating beam can thenbe detected by the rangefinder 19.

[0056] It will be noted that such detection does not require within therangefinder 19 optical means or amplification means other than thoseused for the autonomous mode: detection, in cooperative mode, of theoptical spot formed by the third-party designator takes place underconditions equivalent to the case of designation in autonomous mode.

[0057] Since the designation code used to illuminate the target (NATO,STANAG 3733 or any other code) is known by the rangefinder, theprocessing means T carry out synchronous detection in order to detectthe desired illumination.

[0058] The narrowness of the laser receive field (typically 1 mrad)makes it possible to keep the line of sight of the designator/sight inthe direction of the designated target with precision sufficient for theengagement and the firing having to reach this target.

[0059] To supplement the positional locking that it is thus possible toachieve, the system may also control the motor drive means 111 in orderto introduce slight perturbations in the line of sight and to slave thelatter to the maximum flux in synchronous detection mode.

[0060] Once the sighting/fire control system is locked onto thedesignating spot, the operator may then engage and fire the weapon thatmust be guided onto this spot.

1. A laser sighting system, of the type comprising adesignator/rangefinder (19) comprising means (E) for emitting adesignating beam and receive means (R) for detecting and processing thereflection of a light spot formed by said beam on a target,characterized in that said receive means (R) are capable, in the absenceof a designating beam being emitted by the rangefinder, of detecting thereflection of a light spot formed on a target by a third-partydesignating device, the system including means capable, when the receivemeans of the rangefinder detect such a light spot, of beingautomatically oriented in relation to the direction defined by saidspot.
 2. The system as claimed in claim 1, characterized in that itincludes means (112) capable of slaving the line of sight to the lightspot detected by the receive means of the rangefinder.
 3. The system asclaimed in claim 2, characterized in that the slaving means (112)include means capable of introducing perturbations in the viewingdirection of the rangefinder and of slaving this direction to themaximum detection flux received by the receive means of the rangefinder(19).
 4. The system as claimed in one of the preceding claims,characterized in that it includes a camera display channel (11), theviewing direction of which is aligned with the viewing direction of therangefinder, the rangefinder channel and the display channel beingpartly common.
 5. The system as claimed in claims 3 and 4, characterizedin that the perturbations in the line of sight correspond toperturbations of the order of 1 to 10 pixels on the image recorded bythe camera (11).
 6. The system as claimed in one of the precedingclaims, characterized in that the field of view of the rangefinderchannel is of the order of 1 mrad.
 7. The system as claimed in one ofthe preceding claims, characterized in that it includes means forslaving the line of sight by automatic tracking prior to a light spotbeing detected by the rangefinder.
 8. The system as claimed in one ofthe preceding claims, characterized in that it includes means capable ofverifying a wavelength and/or a code on the light spot detected.
 9. Amethod of designating a target, characterized in that it involves:positioning of the target in the field of view of a system as claimed inone of the preceding claims; emission of a designating beam by athird-party designator onto the target; detection of the spot formed onthe target by said beam; and locking of the target designated by thesighting system.
 10. The method as claimed in claim 9, characterized inthat the target is positioned in the field of view by automatictracking.
 11. A fire control system, characterized in that it includes asighting system as claimed in one of claims 1 to 8 and in that thesystem includes means capable of authorizing the firing of the weaponwhen the receive means of the rangefinder detect such a light spot.